1. Field of the Invention
One embodiment of the present invention relates to a semiconductor device and a method for measuring a current of the semiconductor device.
The present invention relates to an object, a method, or a manufacturing method. In addition, the present invention relates to a process, a machine, manufacture, or a composition of matter. One embodiment of the present invention relates to a display device, a light-emitting device, a power storage device, a memory device, a driving method thereof, or a manufacturing method thereof.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. In some cases, a display device, an electro-optical device, a semiconductor circuit, or an electronic device includes a semiconductor device.
2. Description of the Related Art
Attention has been focused on a technique for forming a transistor using a semiconductor thin film formed over a substrate having an insulating surface (also referred to as thin film transistor (TFT)). Such transistors are applied to a wide range of electronic devices such as an integrated circuit (IC) and an image display device (display device). A semiconductor material typified by silicon is widely known as a material for a semiconductor thin film that can be used for a transistor, and an oxide semiconductor has been attracting attention as well.
For example, a technique for manufacturing a transistor using zinc oxide or an In—Ga—Zn oxide semiconductor is disclosed (see Patent Document 1).
In order to manufacture semiconductor devices that need charge retention, such as liquid crystal display devices, it is very important to know the characteristics of transistors in an off state (hereinafter referred to as off-state current), and the like. This is because the parameters of a thin film transistor such as channel length and channel width are determined in accordance with the characteristics of the transistor in an off state.
Patent Document 2 discloses an evaluation method with which current values lower than or equal to 1×10−24 A can be measured.